Chief executive Peter Wanless explained: "The fact that a young person might hold extreme or radical views is not a safeguarding issue in itself.

"However, when young people are groomed for extremist purposes and encouraged to commit acts that could hurt themselves or others, then it becomes abuse."

The charity said its free, 24-hour service was the first national form of support for parents who either fear their children are being radicalised, or are worried about the impact of international terrorist atrocities.

Warning signs include the youth isolating themselves, talking as if from a script, having outbursts of anger, being disrespectful and asking inappropriate questions. The helpline number is 0808 800 5000.